A novel asymmetric function to improve tension-compression asymmetry and torsion response and its implementation to Auricchio-Petrini model for shape memory alloys

The behavior of shape memory alloys exhibits significant asymmetry under tension, compression, and torsion, posing challenges for accurate modeling in engineering applications. This study introduces a novel approach to improve constitutive models by incorporating an asymmetric function that enables independent parameter definitions for tension, compression, and torsion. This innovation allows material parameters to be determined directly from stress-strain data, enhancing model flexibility and practicality. The proposed method is implemented in the widely used Auricchio-Petrini model, extending its capabilities to capture asymmetry in transformation start stress, hysteresis width, transformation plateau length, and hardening slope, all while maintaining thermomechanical consistency. In the proposed material model, the elastic modulus is differentiated for austenite, multi-variant martensite, and single-variant martensite, with the latter exhibiting an introduced asymmetry. The model also incorporates improved temperature dependency. Validation through comparisons with experimental data demonstrate the model's effectiveness in predicting SMA behavior under diverse proportional and non-proportional loading conditions, including superelasticity and shape memory effects. • Novel asymmetric function improves tension, compression, and torsion responses. • Enhanced Auricchio-Petrini model achieves superior multiaxial response accuracy. • New approach enables high stress asymmetry in tension and compression modelling. • Model parameters derived directly from experimental stress-strain data.